BMW is apparently aware of some issues with their DVD drives. My 2008 M3 worked fine for a few years but then started to have issues reading my burned DVDs, then also the original DVDs. Took it to BMW and they replaced the DVD drive under warranty. The parts manager told me that I was getting a new and improved model, that they had replaced tons of the older model drives. The new drive reads my burned map DVDs just fine, in fact I'm using the 2012 ones with cams as was posted in this thread this spring with no issues at all.
So if you are having issues with your DVD drive, might be worth while getting it replaced with the new model...